More and more users are turning to network-based resources, such as electronic marketplaces, to purchase items (e.g., goods and/or services). Typically, a user (e.g., a customer) may operate a computing device to access a network-based resource and request information about an item. The network-based resource may provide the information and information about an available delivery method. In turn, the user may purchase the item from the network-based resource and specify a delivery location. One delivery option being considered includes delivering items to the delivery location by an unmanned aerial vehicle (UAV). In the future, once the item is loaded on the UAV, the UAV may be configured to navigate to a particular area (e.g., relatively near the delivery location) in order to identify a marker using one or more cameras. Upon detection of the marker, the UAV may navigate to the marker and place the item on or near the marker to complete the delivery. Utilizing UAVs to deliver items to users of an electronic marketplace presents various challenges. For example, the UAV may generally operate at relatively high altitudes, making marker detection difficult. This is especially true in inclement weather. Poor marker detection can cause delivery failure or delay resulting in a negative impact to the electronic marketplace provider such as loss of revenue or good will.